Ooo kkk, colour me thick, but all these children are confusing me too.
Richard and Elizabeth marry in November 1838, and daughter Elizabeth is born December 1839, at which point mother Elizabeth dies, yes? Then, in 1840, little Elizabeth plus three others are all baptised. Who is the mother of the other three? How old are they? Where did you find their baptismal entries and have you seen the actual page or just a transcript?
Four possibilities:
1) Richard Sr has been married before (possibly to an Elizabeth?)
2) Elizabeth has been married before (possibly in Ireland) and the other three are hers but not his, just taking their "new" father's name for the sake of simplicity/ whatever.
3) He has remarried (to another Elizabeth?), and the other three are hers but not his, surname change as above.
4) The other three were born before the marriage.
Have you got a copy of the marriage certificate, and what does that tell us? What about Little Elizabeth's birth and certificates? They could be illuminating too.
Elizabeth dies aged 27, so 2) and 4) are both a possibility.
Regarding the other three children in 1841, they could be with his parents or siblings perhaps? With their birth father's family? With some other Egans somewhere? If they aren't biologically his they may no longer even be calling themselves Blake. Not to mention them possibly being parked somewhere as "nurse" children as suggested, or being in an orphanage of some sort.
